1. The Field of the Invention
This invention relates generally to skin care products, and more particularly to a method by which wrinkles in the skin are smoothed.
2. The Background Art
It is known in the art to use hydroxy acid products to treat human skin. Hydroxy acids are known to "alleviate or improve skin lines; blotches; blemishes; nodules; wrinkles; pigmented spots; atrophy; precancerous lesions; elastotic changes characterized by leathery, coarse, rough, dry and yellowish skin; and other skin changes associated with intrinsic aging or skin damages caused by extrinsic factors such as sunlight, radiations, air pollution, wind, cold, dampness, heat, chemicals, smoke and cigarette smoking." See U.S. Pat. No. 5,547,988 (Yu et al).
Hydroxy acids are effective because the human skin has an inherent (but weak) buffering system that is easily overcome by hydroxy acid formulations that are available over the counter. These formulations have the desired concentration range of hydroxy acids and pH range of products that are intended for unsupervised home use. The mechanism of action for hydroxy acids is not completely understood, but it is known that to be effective in increasing basal cell renewal rates and to be effective in increasing exfoliation times in a cosmetic formulation, the hydroxy acid formulation itself needs to be at a pH of less than 4.0 regardless of the acid concentration. Hydroxy acid formulations with a pH of less than 3.0 may be effective, but should not be considered for unsupervised home use and formulations with a pH higher than 4.0 will generally have little if any effect on skin physiology. Once the hydroxy acid formulation contacts the skin there is an almost immediate yet transient decrease in skin pH. The amount of time (anywhere from 20 minutes to 2 hours) that skin pH is lowered below the normal range of 4.5 to 6.0 will vary from person to person.
In 1997, the Food and Drug Administration (FDA) published its findings on the safety of alpha hydroxy acid products. To summarize, the FDA declared alpha hydroxy acid products safe for unsupervised use at concentrations of no more than 10% and at a pH of no less than 3.5. However, it may be possible to use products containing 10% or more acids when the products in this concentration range are generally at a pH of less than 3.0. Furthermore, products containing 10% or more acids can be used continuously with continued benefits to the skin. However, these products are more likely to cause problems for the user, i.e., burning, stinging, erythema, irritation, etc. The acids making up the 10% concentration are glycolic and lactic.
It is well known that human skin will stop or be slower in responding to cell renewal stimulation after 4 to 8 weeks of continued use of topically applied hydroxy acids. The skin gradually strengthens its buffering system to adapt to the daily assault from hydroxy acids so that any effect the acids have on skin physiology is eventually nullified. To regain the buffering system that allows for beneficial cell renewal stimulation, the skin should be allowed to rest from hydroxy acid use for a period of 4 to 6 weeks. This rest allows the buffering system to return to normal and the process can be started again.
A significant problem of the prior art is that most of the improvements in the skin condition that are made through the hydroxy acid treatments in the first 4 to 8 weeks are lost during the rest period in the next 4 to 6 weeks. During the rest period, the skin tends to return to its original state so that when the buffering system returns to normal the beneficial effects that were realized in the skin during the first 4 to 8 weeks are no longer apparent. The cell renewal stimulation process is once again at or very near the original state of the skin.
The '988 (Yu et al) patent teaches a method for improving the skin condition of a human. Although the '988 patent does not mention a particular pH to be used in the hydroxy acid formulation, the patent mentions a formulation containing at least a 5.0% concentration of hydroxy acid or its derivative. In fact, the '988 patent teaches that the hydroxy concentration is "preferably between 8 to 20%." Column 14, lines 28-30. In addition, the '988 patent teaches that "Blotches, blemishes, nodules, age spots, pigmented spots, skin lines, and fine wrinkles improved or disappeared" three to five months after the recommended treatment. Column 15, lines 39-42. The '988 patent also teaches application of the hydroxy acid product on a daily basis without rest periods for the skin. Column 18, lines 17-18.
Yu et al are the inventors of another related invention described in U.S. Pat. No. 5,422,370 (the '370 patent). The '370 patent teaches a method to improve dry and flaky skin using a product having 3% to 7% hydroxy acids. Column 15, lines 52-64. The '370 patent does not teach a specific amount of topical lotion to be applied nor a specific time period for which the lotion should be applied. See column 20, lines 52-56. The length of time the lotion is applied is indefinite, being stated as one to three weeks for improvements in age spots (column 18, line 29), one to three months for substantial eradication of age spots (column 18, lines 30-31), and two to four months for complete eradication of age spots (column 18, lines 33-35). The '370 patent also states that a composition with a 10% to 20% concentration of hydroxy acids is preferable when treating wrinkles but that favorable results do not occur within four months of time. Column 18, lines 35-43. The '370 patent does not disclose alternating hydroxy acid use with rest periods for improvements in skin condition.
Of current interest is a cell renewal stimulation process that preserves skin improvements that are realized through treatments with hydroxy acid products when the use of the hydroxy acid products is alternated with a rest period.